Chain jack

ABSTRACT

Chain jack for the tightening of chains, comprising an upper stopper unit (20) and a lower stopper unit (30) with opposite locking pawls where each can be locked to a through-running chain (12) so that they can be detached, and also several drive units (50; 150) to push the upper and lower stopper units (20,30) mutually towards and away from each other, in which the upper and lower stopper units (20,30) each comprises two pairs of locking pawls (20a,20b;22a,22b and 30a,30b;32a,32b, respectively) which engage with mutually adjoining links (12a, 12b, . . . ) in the chain link (12), is described.

AREA OF THE INVENTION

The present invention relates to a new type of chain jack that shall be used to tighten and hold anchor lines on board anchored, floating installations.

In more detail the invention relates to a chain jack comprising upper and lower stopper units which, with facing locking pawls each of which can be made loose, can be locked to a through-running chain, and also a drive unit to push the stopper units mutually to and from each other. In more detail, two types of drive units to push the stopper units mutually to and from each other are proposed according to the invention, and also to push the facing locking pawls towards and away from each other.

BACKGROUND OF THE INVENTION/DESCRIPTION OF PRIOR ART

Different constructions of jacks are known in connection with handling of chains to anchor floating installations, and they are also used to tighten up anchor lines. Applications of the construction during towing of larger installations with chains can also be imagined.

Normally such jacks are composed of one or two cylinders with only one pair with locking pawls on the upper and lower stoppers, and also in-between lying cylinders that are used to push the stoppers from each other when the chain is tightened and also to pull the stoppers together again to a new starting position and pushing out steps. By alternating locking and releasing, respectively, of the grip of the upper and lower stoppers about the chain, this can be led through the jack and be tightened.

As the stoppers in the construction only comprise their own locking pawl pair, this leads to the locking pawls only being able to engage with every other chain loop and they must therefore have a double length stroke on the vertical cylinders.

From the patent literature, reference is made to US 2014/026796 A1 relating to a chain jack for the tightening of a chain, and also U.S. Pat. No. 5,934,216 A that shows a device for tightening and mooring of a chain with a chain jack.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a new stopper construction for a chain jack.

It is a further object of the invention to provide a new shape of the locking pawls of the stopper units so that they can form an engagement with the underside of each link (mutually turned 90° away from each other) in the chain.

One main object of the new construction of the jack is to reduce the theoretical stroke length of the vertical drive units (hydraulically, possible electrically driven) in that the locking pawls of the stopper units can form said engagement with each individual link that passes through the chain jack.

It is a further object to provide a new solution for a chain jack with regard to the number and placing of the drive units (hydraulically, possibly electrically driven) that pushes the stopper units out and pulls them back in the chain jack, i.e. up to and out from the engagement with the underside of the links in the chain.

Release and movement of jacks are known from before. After the chain has been tightened, it is cut some loops over the loop that is locked in the lower stopper unit. The chain is then placed down onto the deck before the jack is moved to the next anchor line.

The chain jack is preferably driven by four drive units, such as with hydraulic pressure cylinders or with electrically driven threaded struts and it has a double set of locking pawls in each stopper unit.

A practical and possibly preferred solution then means four drive units/cylinders (one cylinder in each corner). That the chain jack is driven by four cylinders instead of two is an advantage in connection with maintenance and provides increased security with respect to leaks and breaks in operation. Then it will be possible to dismantle one cylinder/drive unit without removing the chain and it will be possible to operate the chain jack with reduced power with only three of the four cylinders in operation.

However, the chain jack will also be able to operate with two drive units/cylinders to operate both locking pawls.

SUMMARY OF THE INVENTION

The above mentioned objects are achieved with a chain jack for the tightening of a chain, comprising an upper stopper unit and a lower stopper unit with opposite locking pawls that can be locked to a through-running chain so that it can be released, and also several drive units to push the upper and lower stopper units mutually towards and away from each other. Both the upper and lower stopper units comprises two pairs of locking pawls that engage with mutually adjoining links in the chain.

In a first embodiment, the drive unit is made up of several hydraulic pressure cylinders that provide said mutual movement of the upper and lower stopper units.

In a second embodiment, the drive unit is made up of several electrically driven threaded struts that provide said mutual movement of the upper and lower stopper units.

Each locking pawl pair in a stopper unit can be set at a mutual angle of 90° to each other, to alternately engage with the underside of two adjoining links in the chain during its forwards movement through the jack.

Furthermore, four locking pawls in each stopper unit can operate in pairs of two in the same plane against the chain.

Each locking pawl in a locking pawl pair can form, in a known way, respective recesses to support and lock against the underside of respective links in the chain.

The lower stopper unit can be fastened to a foundation, such as a deck of a ship or platform.

The upper stopper unit with its locking pawls can be anchored to the top part of the drive units which, in a first embodiment, is made up of several hydraulic pressure cylinders and which provides said mutual movement of the two stopper units.

The pressure cylinder of the upper stopper unit can rest on a seat in a plinth plate of the lower stopper unit.

The upper stopper unit with the pressure cylinders can be detachably anchored to the plinth plate of the lower stopper unit and thus set up to be released from the lower stopper unit.

Under the lower stopper unit two pairs of load cells can be fitted for continuous monitoring of the tension in the chain, as two individual load cell pairs means that the solution has full redundancy, with one set in reserve if the other fails. This is the case for all variants of the invention.

The tension in the chain can, for example, be calculated from the oil pressure in the cylinders when hydraulic cylinders are used.

The drive units to mutually push the stopper units towards and away from each other can, in another embodiment, be made up of several threaded struts that are driven by their own electro-motor, as the lower stopper unit is stationary in a frame section, while the upper stopper unit is set up to be driven/pushed upwards or downwards with respective threaded struts when these are rotated by respective electro-motors.

The upper stopper unit can be set up to be pushed upwards and downwards in longitudinally-running, regulating and steering grooves in the frame section to be able to be screwed upwards and downwards by the threaded struts.

Both a top part and the plinth plate in the frame section can centrally define a cross-formed through-run for the chain.

Each locking pawl in the two pawl pairs can be pushed inwards and be retracted with the help of associated electrical actuators, such as linear actuators that function in analogue to the hydraulic actuators.

Each threaded strut can be coupled to respective electro-motors via associated planet gear fitted below the electro-motor, as it is connected between the exit shaft from the above lying electro-motor and the threaded strut from the underside, as the planet gears are used to gear the torque moment and the number of revolutions of the motor to what the threaded strut requires.

Four electro-motors can be arranged in the top part of the drive unit, preferably in each corner of the top part of the frame to drive associated four threaded struts that can provide said mutual movement of the two stopper units.

DESCRIPTION OF THE FIGURES

Preferred embodiments of the invention shall now be described in the following in more detail with reference to the enclosed figures,

FIG. 1 shows in perspective the shape of an assembled chain jack with a through-running chain that shall be tightened according to the invention comprising an upper and a lower stopper unit, each with two pairs of hydraulically operated locking struts, in that the two stopping units are pulled together to exert the next step in a lifting process of the through-running chain. The lower stopping unit is fastened to a solid foundation to be able to exert its function.

FIG. 2 shows a vertical side outline of an upper stopper unit with its two pairs of locking pawls and vertical lifting cylinders, in more detail in a situation where the upper stopper unit is disconnected from the lower stopper unit and released from the chain itself, for example, to be removed for handling of a different chain.

FIG. 3 shows a perspective of the construction of the lower stopper unit with locking pawls and load cells, for example, when the upper stopper unit (FIG. 2) is disconnected to operate the next anchorage chain.

FIG. 4 shows a vertical perspective of upper and lower stopper units that are pulled together completely. With further reference to FIG. 4, a vertical outline of a jack corresponding to the jack in FIG. 1, the one pair of locking pawl pairs is in a lower stopper unit, in engagement with the underside of one link of the chain and holds the chain, while the upper stopper unit with its corresponding pair of locking pawls, from an open/released position is about to be pushed towards each other to form a new engagement under the above-lying link in the chain for the next pushing out/lifting of this.

FIG. 5 shows, corresponding to FIG. 4 but where the one pair of locking pawls of the upper stopper unit engages under a chain link and is pushed out into its extended position. The one lower pair of locking pawls is open while the pair of locking pawls that stands 90° to the lower stopper unit is closed and ready to take over the load.

FIGS. 6 and 7 show vertical sections, partially in outline of an alternative embodiment of a chain jack according to the invention, with upper and lower stopper units and also electro-motors fitted to the top of the frame. The figures show the same frame unit from two sides that are standing 90° to each other.

FIG. 8 shows a perspective of the alternative construction.

FIG. 9 shows a plane outline of the construction, i.e. the frame with the four electro-motors placed in separate corners, and also the central cross in the middle that represents the chain which runs centrally through the frame.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Reference is initially made to the FIGS. 1 and 4, which in perspective and in longitudinal section, respectively, show the assembled chain jack 10, and also the through-running chain 12 that is being tackled. The jack 10 comprises an upper stopper unit 20 and a lower stopper unit 30, each with two pairs of hydraulically operated locking pawls 20 a,20 b,22 a,22 b, and 30 a,30 b,32 a,32 b, respectively, and also in-between lying hydraulic cylinders 50 with cylinder struts 52. The four locking pawls in each stopper unit are set up to work two and two in a pair in the same plane against the chain links. The locking pawls 20 a,20 b make up a first pair of locking pawls in the upper stopper unit 20, while the locking pawls 22 a,22 b make up a second pair of locking pawls in the upper stopper unit 20. The locking pawls 30 a,30 b make up a first pair of locking pawls in the lower stopper unit 30, while the locking pawls 32 a,32 b make up a second pair of locking pawls in the lower stopper unit 30.

The upper locking pawl pair is also shown by 20 a-20 b and 22 a-22 b, respectively, and the lower pair of locking pawls is shown by 30 a-30 b and 32 a-32 b, respectively.

Each pair of locking pawls is set up 90° to each other to alternatively form a locking engagement with the underside of respective links in the chain. Each of the four locking pawls in the upper stopper unit 20 is mounted in an upper holding frame 54 in a rotary point 36 (FIG. 4) and is rotated in and out of the chain link-locking engagement about the point of rotation with the help of hydraulic cylinders 38. The holding frame 54 rests uppermost on the cylinder struts 52 (FIGS. 4 and 5) that can be pushed out and pulled back in associated cylinders 50.

Correspondingly, the pair of locking pawls in the lower stopping unit 30 is mounted to be swung into and out of a locking engagement with the help of hydraulic cylinders 38. These pairs of locking pawls are further mounted to a plinth plate 40, which in turn is anchored to a foundation associated with the installation (the deck or the like).

Both the holding frame 54 and the plinth plate 40 comprise a cross-formed opening centrally in the jack for the bringing forth of the chain 12 and holding it in a stable position to avoid twisting.

The figures also show the dish-formed rounded end 39 a,39 b of the locking pawls which take up and form an engagement with the rounded underside of the chain link 12 c, as the locking takes place when two opposite ends of locking pawls 39 a,39 b squeeze against the underside of the chain link from either side. In this position one sees (FIGS. 4 and 5) that the underside of the locking pawl also grips/pushes into the next link 12 d that is turned 90° and hangs in the link 12 c.

Mutual Assembly of Stopper Units

FIG. 2 shows the upper stopper unit 20 with its pair of locking pawls 20 a,20 b;22 a,22 b and also the hydraulic cylinders 50 being fitted to and extending down to the bottom parts 43 that shall rest against a foundation/seat 41 on a plinth plate 40 of the lower stopper unit 30.

FIG. 3 shows the lower stopper unit 30 with its pair of locking pawls 30 a,30 b;32 a,32 b fitted on the plinth plate 40 of the installation and which also forms a cross-formed (+) central opening in the jack to guide the chain 12 and prevent it rotating.

The plinth plate 40 of the lower stopper unit 30 forms, in this case, four seats 41 (FIG. 3), one in each corner, to receive the bottom part 43 of the four hydraulic cylinders 50 around the circumference.

In FIG. 3 the locking pawls 32 a 32 b are pulled back from the engagement, while the locking pawls 30 a,30 b are push forwards to engage in under the link 12 g in the chain. This is the situation when the chain hangs in the lower stopper unit 30 while the upper stopper unit 20 is released and pulled down into a retracted position with the help of the four hydraulic cylinders 50.

Thus each underside of the cylinders 50 (FIG. 2) rests on the seat 41 of the plinth plate 40, while the extendable cylinder struts 52 (completely pushed into the cylinder 50 in FIG. 1) are fastened uppermost in a seat that carries the upper stopper unit 20 via the holding frame 54 in the form of a square plate. According to the invention the hydraulic cylinders 50 are detachably fastened in the seat 41 with a suitable screw connection, so that they can easily be released from the plinth plate 40 and be moved to work on a different chain.

Furthermore, the plinth plate 40 is anchored to a foundation on an installation, floating platform or a ship, something which is not shown here.

Application of the Invention

FIG. 4 shows the jack retracted and FIG. 5 shows it completely extended with its full stroke length. When the chain 12 shall be pulled through the jack in the direction of the arrow P in FIG. 4, the stopper units 20,30 are pulled together to a position shown in the FIGS. 1 and 4. Thereafter the one pair, see FIG. 4, fixedly grips with the locking pawls 22 a,22 b (or 20 a,20 b) onto the upper stopper unit 20 on the underside of the link 12 c, while the locking pawls 30 a,30 b,32 a,32 b of the lower stopper unit 30 are reset into an open position. Then the cylinders 50 are pressurised so that the respective cylinder strut 52 is pushed out and lifts the upper stopper unit 20 and the chain 12 upwards. The locking pawls of the lower stopper unit 30 are not opened before they are relieved of a load, i.e. after the locking pawls of the upper stopper unit 20 has taken over the load and pushed the chain upwards.

When the chain is lifted a height corresponding to a link 12 c in FIG. 4, plus a small clearance, the opposite pair of locking pawls 30 a,30 b on the lower stopper unit 30 locks a grip in the underside of the associated link 12 g further down the chain 12 at the same time as the upper locking pawls 20 a,20 b,22 a,22 b, are relieved of a load in that the vertical cylinder struts 52 are driven down somewhat. This sequence is repeated link for link in the chain until the chain 12 has been tightened as required. To obtain the exact pretension, this can be carried out on each link (loop) in the chain.

Under each of the upper 20 and lower stopper units 30, two pairs of load cells are fitted which monitor the tension on the anchor chain all the time. The use of two individual load cell pairs means that the solution has full redundancy so that one always has a set in reserve if the other should fail.

When the load is transferred to the upper stopper unit 20, the tension in the chain is calculated according to the oil pressure in the cylinders 50. The use of four vertical cylinders makes it possible to carry out service on one cylinder while the arrangement is kept by the three others, i.e. the jack can handle and tighten the chain even if one of the cylinders is out of operation for maintenance and replacement. The operator controls the tension in the chain via the oil pressure that is registered in the pressure cylinders with the help of pressure sensors.

The solution is manufactured so that the upper stopper unit 20, including the vertical hydraulic cylinders 50, is detachably assembled with the lower stopper unit 30, and this can thereby be moved to the next anchor line after a complete tightening operation. The FIGS. 2 and 3 illustrate the upper and lower stopper units disengaged. The lower stopper unit 30 with the load cells remains standing locked again and holds the chain 12 as shown in FIG. 3.

This means that the jack mechanism of the upper stopper unit 20 itself can be used on several anchor lines 12. At the same time all anchor lines must have a lower stopper unit 30, possibly with load cells.

The locking pawls are driven by hydraulic cylinders and the movement is regulated by parallel struts. This ensures that the locking pawls 20 a,20 b,22 a,22 b; 30 a,30 b,32 a,32 b can be moved swiftly out of an engagement so that the extra stroke length on the vertical cylinders to obtain sufficient clearing between the chain 12 and the locking pawls is reduced to a minimum, The locking pawls also have an ideal contact with the foundation which means that the forces are more effectively transferred as surface pressure without bending tension in the locking pawls.

In summary, there are many advantages with the present solution:

-   -   Compact construction dimensions     -   Low weight     -   Short stroke length     -   Can grip each loop in the chain 12, something which means         greater possibilities of more accurate pretension of the chain     -   Use of four vertical cylinders gives the possibility to carry         out service on one cylinder while the arrangement is held and         can be operated by the other three.     -   Stable solution which can readily be secured to the foundation     -   An upper stopper unit 20 with vertical cylinders 50 can easily         be moved from anchor line to anchor line.     -   Locking pawls are regulated by parallel struts to optimise the         stroke length of the vertical cylinders.     -   Efficient power transmission in the form of surface pressure         against the foundation without bending tensions in the locking         pawls.

Alternative Variant of the Chain Jack

According to an alternative solution the construction is changed so that the pressure cylinders are replaced by threaded struts which, with the help of electro-motors, are rotated to raise and lower the upper stopper unit and shall be described in connection with the FIGS. 6-9.

The locking pawl pairs 20 a,20 b;22 a,22 b in the upper stopper unit 20 and the locking pawl pairs 30 a,30 b;32 a,32 b in the lower stopper unit 30 are designed and are operated in the same way as explained earlier.

The chain jack comprises a frame 100 in the form of, for example, a truss frame, preferably square, with vertical struts and a bottom part/plinth plate 40 to which the lower stopper unit 30 is fixed. The upper stopper unit 20 can be moved up and down in the frame in that it is moved with the help of four threaded struts 180,182,184,186 each of which is rotated with the help of their own electro-motor 102,104,106,108 that is fitted at the top of the roof section 110 of the frame 100. The threaded struts 180,182,184,186 run through correspondingly formed threaded borings through the holding frame 54 to the upper stopper unit 20, i.e. a threaded boring at each corner of the holding frame 54, so that when the threaded struts are synchronously rotated the stopper unit 20 is displaced up/down depending on the direction of rotation. The lower end of each threaded strut 180,182,184,186 is mounted in a recess (not shown) in the lower plinth plate/bottom part 40 so that it can rotate. The upper stopper unit 20 is lifted upwards to lead the chain 12 upwards through the jack, so that the chain link is tightened.

At each corner of the upper stopper unit 20 outwardly extending pegs are formed that extend into vertical, longitudinally-running guiding grooves in the vertical beams in the frame section so that the stopper unit 20 is stabilised in its upwards and downwards movement in the frame 100.

In an alternative embodiment each corner of the upper stopper unit 20 can be formed with gliding surfaces that lie against the vertical beams in the frame section so that the stopper unit 20 is stabilised in its upwards and downwards movement in the frame 100.

As shown in FIG. 9, both the top part and the bottom part of the frame section define a central, cross-formed through run for the chain.

Between the exit shaft from each drive motor 102,104,106,108 and associated threaded struts 180,182,184,186 (i.e. under the el-motor) a planet gear 160 is coupled in that it has as an aim to gear the torque moment and revolutions of the motor to what the threaded strut requires.

Both the upper 20 and lower 39 stopper units comprises two locking pawl pairs, which are the first examples with hydraulic drive cylinders. Each locking pawl in a pair can be pushed inwards and pulled back with the help of associated electrical actuators, such as linear actuators that function in analogue with hydraulic actuators.

The perspective in FIG. 8 and the plane outline in FIG. 9 clearly show the placing of the four electro-motors 102-108 in the top part of the frame 100.

As in the first version, two load cells are fitted under the lower stopper unit 30 to exert a continuous monitoring of the tension in the chain, as two individual pairs of load cells mean that the solution has full redundancy with one set in reserve if the first set fails. 

1.-19. (canceled)
 20. A chain jack for tightening of a chain, comprising an upper stopper unit and a lower stopper unit with opposite locking pawls, where each locking pawl is detachable locked to a through-running chain, several drive units pushing the upper and lower stopper units mutually towards and away from each other, wherein the chain jack comprises four drive units, one in each corner of the chain jack, providing said mutual movement of the upper and lower stopper units, and the upper and lower stopper units each comprise two pairs of locking pawls, respectively, which engage with mutually adjoining links in the chain link.
 21. The chain jack according to claim 20, wherein each pair of the locking pawls in a stopper unit has a mutual angle of 90° to each other to alternately engage with the underside of two adjoining links in the chain during its travel through the jack.
 22. The chain jack according to claim 20, wherein four locking pawls in each stopper unit operate in pairs two by two in the same plane against the chain.
 23. The chain jack according to claim 20, wherein each locking pawl in a pair of locking pawls provide respective recesses to push and lock against the underside of respective links in the chain.
 24. The chain jack according to claim 20, wherein the lower stopper unit is secured to a foundation, such as a deck of a ship or a platform.
 25. The chain jack according to claim 20, wherein the upper stopper unit with its locking pawls are anchored to a top part of the drive units, that is made up of several hydraulic cylinders, and which provide said mutual movement of the upper and lower stopper units.
 26. The chain jack according to claim 25, wherein the hydraulic cylinders of the upper stopper unit rest on a seat in a plinth plate of the lower stopper unit.
 27. The chain jack according to the claim 26, wherein the upper stopper unit with the hydraulic cylinders are anchored detachably to the plinth plate of the lower stopper unit.
 28. The chain jack according to claim 20, wherein two pairs of load cells for continuous monitoring of the tension in the chain are fitted below the lower stopper unit, providing two individual pairs of load cells with full redundancy, with one set in reserve if the other fails.
 29. The chain jack according to claim 25, wherein chain tension is calculated according to oil pressure in the hydraulic cylinders.
 30. The chain jack according to claim 20, wherein each drive unit to mutually push the upper and lower stopper units towards and away from each other comprises a threaded strut that is driven by an individual electro-motor, and the lower stopper unit is stationary in a frame section while the upper stopper unit is movably upwards or downwards with respective threaded struts when these are rotated by the respective electro-motors.
 31. The chain jack according to claim 30, wherein the upper stopper unit is guided upwards and downwards in longitudinally running steering and guiding grooves in the frame section and is screwed upwards and downwards by the threaded struts.
 32. The chain jack according to claim 30, wherein a top part and a plinth plate of the frame section define a centrally cross-formed through-run (+) for the chain.
 33. The chain jack according to claim 30, wherein each locking pawl is pushed inwards and pulled back with the help of associated electrical actuators, such as linear actuators that function in analogue with hydraulic motors.
 34. The chain jack according to claim 30, wherein each threaded strut is coupled to respective electro-motors via an associated planet gear fitted under the electro-motor, and is coupled between the exit shaft from the above-lying electro-motor and the threaded strut from the underside, and wherein the planet gears are adjusting torque moment and revolutions of the motor to what the threaded strut requires.
 35. The chain jack according to claim 30, wherein four electro-motors are placed in the top part of the drive units, preferably in each corner of a top part of the frame section to drive the associated four threaded struts that provide said mutual movements of the upper and lower stopper units.
 36. The chain jack according to claim 20, wherein each drive unit is a hydraulic pressure cylinder which provide said mutual movements of the upper and lower stopper units.
 37. The chain jack according to claim 20, wherein each drive unit is an electrically driven threaded struts which provide said mutual movements of the upper and lower stopper units. 